Virtual monoenergetic images and post-processing algorithms effectively reduce CT artifacts from intracranial aneurysm treatment

David Zopfs,Simon Lennartz,Thorsten Persigehl,Lenhard Pennig,Jan Borggrefe,Andreas Glauner,Nils Große Hokamp,Nuran Abdullayev,Christoph Kabbasch,Johannes Bremm,Kai Roman Laukamp

doi:10.1038/s41598-020-63574-8

Abstract

To evaluate artifact reduction by virtual monoenergetic images (VMI) and metal artifact reduction algorithms (MAR) as well as the combination of both approaches (VMIMAR) compared to conventional CT images (CI) as standard of reference. In this retrospective study, 35 patients were included who underwent spectral-detector CT (SDCT) with additional MAR-reconstructions due to artifacts from coils or clips. CI, VMI, MAR and VMIMAR (range: 100–200 keV, 10 keV-increment) were reconstructed. Region-of-interest based objective analysis was performed by assessing mean and standard deviation of attenuation (HU) in hypo- and hyperdense artifacts from coils and clips. Visually, extent of artifact reduction and diagnostic assessment were rated. Compared to CI, VMI ≥ 100 keV, MAR and VMIMAR between 100–200 keV increased attenuation in hypoattenuating artifacts (CI/VMI200keV/MAR/VMIMAR200keV, HU: −77.6 ± 81.1/−65.1 ± 103.2/−36.9 ± 27.7/−21.1 ± 26.7) and decreased attenuation in hyperattenuating artifacts (HU: 47.4 ± 32.3/42.1 ± 50.2/29.5 ± 18.9/20.8 ± 25.8). However, differences were only significant for MAR in hypodense and VMIMAR in hypo- and hyperdense artifacts (p < 0.05). Visually, hypo- and hyperdense artifacts were significantly reduced compared to CI by VMI≥140/100keV, MAR and VMIMAR≥100keV. Diagnostic assessment of surrounding brain tissue was significantly improved in VMI≥100keV, MAR and VMIMAR≥100keV. The combination of VMI and MAR facilitates a significant reduction of artifacts adjacent to intracranial coils and clips. Hence, if available, these techniques should be combined for optimal reduction of artifacts following intracranial aneurysm treatment.

Highlights

To evaluate artifact reduction by virtual monoenergetic images (VMI) and metal artifact reduction algorithms (MAR) as well as the combination of both approaches (VMIMAR) compared to conventional computed tomography (CT) images (CI) as standard of reference
Recent studies suggested that combined application of MAR and virtual monoenergetic images (VMI) derived from dual-layer spectral-detector CT (SDCT) may be more effective than individual application of these techniques in different settings17,21
The purpose of this study was to investigate the potential of SDCT derived VMI and MAR reconstructions as a single approach as well as their combination (VMIMAR) for metal artifact reduction in patients who underwent intracranial coiling or clipping

Summary

Results

Our included 35 patients comprised 25 women and 10 men with a mean age of 56.8 ± 13.1 years, ranging from 32–84 years. Combination of VMI and MAR at all keV levels significantly increased corrected attenuation in hypodense (VMIMAR200keV: −21.1 ± 26.7 HU) and decreased corrected attenuation in hyperdense artifacts (20.8 ± 25.8 HU, Fig. 1, Table 1). Compared to CI, corrected image noise slightly decreased in hypodense artifacts in VMI ≥ 100 keV and slightly increased in hyperdense artifacts in VMI at all keV-values; differences were not significant. MAR alone and in combination with VMI at all keV-levels significantly decreased corrected image noise compared to CI (CI/VMIMAR200keV, hypodense: 35.9 ± 35.4/8.9 ± 8.0 HU; hyperdense: 17.5 ± 13.8/7.2 ± 8.1 HU, Fig. 2, Table 1). Diagnostic assessment of brain tissue adjacent to coils or clips was significantly improved in VMI ≥ 100 keV, MAR and combination of VMI and MAR (VMIMAR). Overall interrater agreement was good (intraclass correlation coefficient: 0.66, Table 2)

Discussion

Conclusion

Methods